PD: Arrests made in shooting death of MCSO detention officer

Jorge Vargas, a county jail detention officer, was shot and killed in the driveway of his home Aug. 8. (Source: Maricopa County Sheriff's Office)

Ivan Montes was another suspect taken into custody. (Source: Maricopa County Sheriff's Office)

Catherine Seymour (Source: Maricopa County Sheriff's Office)

Leonard Moreno, 15, is one of those arrested. (Source: Maricopa County Sheriff's Office)

Vargas was working on his truck in the driveway before going to work when he was shot. (Source: CBS 5 News)

PHOENIX (CBS5) -

He is only 15 years old, but the boy who was arrested in the ambush shooting death of a Maricopa County detention officer in August already has a lengthy career in crime.

Police Chief Daniel Garcia said Wednesday that Leonard Moreno will be charged as an adult with first-degree murder in the shooting of 27-year-old Jorge Vargas.

Police said two days after Vargas' death, Moreno was involved and later arrested in a drive-by shooting after a party at a west Phoenix home.

"Leonard Moreno wanted to be a gang member," Garcia said. "Leonard Moreno is a drug user and drug seller, and he acquired a weapon. These three categories put together on Aug. 8 result in the tragic senseless death of Jorge Vargas."

Several other people were also arrested in connection with Vargas' death. They are Ivan Montes, 20, for hindering prosecution and disorderly conduct, and Moreno's mother, Cathy Seymour, for hindering prosecution. Seymour has since been released from jail after posting bond.

Another juvenile was arrested in this case. Police said they expect more arrests to be made.

Evidence recovered from that scene linked Moreno to the crime, according to a court document.

Bullet casings from the Vargas shooting were tied to a suicide attempt Jan. 2 by Montes. A witness told police that Montes later sold the handgun to Moreno in May or June.

Moreno's Instagram account revealed he bought the gun for $350, and later posted more pictures of himself with the gun, according to the document.

After he shot Vargas, Moreno fired shots into other vehicles at the scene and DNA on the shell casings were matched to Moreno, according to the document.

A witness told police Moreno's family said he came home that morning out of breath and sweating and said he had been at a party with the gun, according to the document.

He then posted on Instagram another picture with the gun and the caption, "Did it once for fun. Don't make me do it again n be serious haa (; #RT "

Moreno has a long list of run-ins with the law.

When he was just 9 years old in 2007 he was arrested for burglary, criminal damage and criminal trespassing.

Court records show he also admitted to marijuana possession 2011.

In 2012, he was arrested on a number of charges, including assault, and in 2013 he faced a number of drug charges.

Police said it the Vargas shooting appeared to be random and that Vargas was not targeted because of his position.

Vargas was shot multiple times while working on his truck in the driveway of his Phoenix home before going to work the morning of Aug. 8.

He was an eight-year veteran with Maricopa County Sheriff's Office, assigned to the Custody Support Bureau.

Vargas' body was found by neighbors about 4 a.m. in the driveway of his home near 91st Avenue and Durango Street, south of Buckeye Road, according to Phoenix police.

A neighbor told CBS 5 News she was leaving for work when she heard gunshots and saw the suspect run away.

"Just when I walked out the door, I heard three shots go off and it scared me because that's how close it was," said the neighbor who did not want to be identified. "It was really loud."

She said she ran to Vargas to help and called 911.

An extensive ground and air search Thursday morning proved fruitless.

Crump said neighbors said a man was seen running from the scene. He was described as Hispanic, in his 20s, with black hair and between 155 and 160 pounds. He was seen wearing a white T-shirt and black shorts.

Vargas was taken to St. Joseph's Hospital and Medical Center in Phoenix, where he died.

He is survived by his wife and young son.

The neighborhood where the shooting occurred uses Tolleson addresses, but is within Phoenix and under Phoenix PD jurisdiction.